Bonus Tax: Aggregate vs Percentage Method (2026) — Which One Hits Harder

Two employees at the same company get a $20,000 year-end bonus on the same payday. One ends up with a federal withholding line that reads $4,400. The other's reads $6,800. Both are correct. The difference is the method the payroll system used — the percentage method or the aggregate method — and the choice is governed by a single line in Treas. Reg. § 31.3402(g)-1.

This article walks through both methods with real paystub math, explains when an employer is locked into one or the other, and shows you how to read which method hit your last bonus. For the broader picture of how bonuses get taxed — including the 22% to 37% switch at the $1M threshold — start with the bonus tax calculator, then come back here for the methodology piece.

The Two Methods at a Glance

IRS Publication 15 (the Employer's Tax Guide) lays out exactly two ways an employer can withhold federal income tax on supplemental wages — bonuses, commissions, severance, retroactive pay, accumulated PTO payouts, and anything else paid outside the regular wage stream.

• Percentage method (the flat-rate route). Apply a flat 22% federal withholding rate to the bonus, regardless of the employee's W-4 or regular paycheck. If the cumulative supplemental wages from this employer have exceeded $1,000,000 in the calendar year, apply 37% to the excess portion instead.
• Aggregate method (the run-through-the-tables route). Add the bonus to the most recent regular paycheck. Look up the combined gross in the IRS Publication 15-T withholding tables for that pay period. Compute the total tax that would be withheld on the combined amount. Subtract the tax already withheld on the regular paycheck. The remainder is the bonus withholding.

The percentage method is calendar-time arithmetic. The aggregate method is a projection — it asks “what if this combined paycheck were typical for the year?” and runs that hypothetical through the marginal brackets.

Worked Example: $20,000 Bonus on a $7,000 Biweekly Paycheck

Same employee, same bonus, same pay period. Single filer, no dependents, claiming standard deduction on W-4. Both methods are calculated against the 2026 IRS Publication 15-T tables (Annual Percentage Method tables for biweekly pay frequency).

Method 1: Percentage Method

Method 2: Aggregate Method

Combined paycheck: $7,000 regular + $20,000 bonus = $27,000 for the biweekly period. Annualized projection: $702,000.

The aggregate method withholds $2,400 more federal tax on the same $20,000 bonus, simply because the table-lookup projection assumes the combined paycheck is typical. The employee gets that money back at tax filing — but the immediate paycheck hit is real, and the cash-flow difference matters when people are budgeting for end-of-year purchases.

When the Employer Has a Choice — and When They Don't

The regulatory text is in Treas. Reg. § 31.3402(g)-1(a)(7), backed up by the 2026 edition of IRS Publication 15:

• Separate supplemental check, bonus identified separately. Either method is allowed. Most employers default to the percentage method here because it's simpler and produces a cleaner paystub.
• Combined paycheck with the bonus blended into regular wages. Aggregate method only. The percentage method requires the supplemental wages to be identified separately from regular wages in payroll records. If they're combined on one line, the IRS treats the entire payment as regular wages for withholding purposes.
• Year-to-date supplemental wages above $1M. The 37% mandatory flat rate kicks in on the excess regardless of method. See the 22% vs 37% bonus tax article for the full $1M threshold rules.

Employers tend to pick the method that produces less HR friction. Big tech and finance shops with stock-based comp (RSUs, ESPP true-ups) usually run the percentage method because it generalizes cleanly across equity events. Smaller employers with a single annual bonus cycle often use the aggregate method by default because their payroll system bundles bonus into the December paycheck automatically.

Why the Aggregate Method Overshoots

The Pub 15-T tables are designed under one assumption: this paycheck is representative of every paycheck this year. Once that assumption breaks — as it does on any month containing a one-off bonus — the projection lands in a tax bracket higher than the employee's real annual situation.

For the $27,000 combined biweekly example above, the annualized projection of $702,000 falls deep in the 37% federal bracket. The marginal rate applied to the bonus portion is around 35-37%. But if the employee's actual full-year W-2 ends up at $200,000, their real top marginal bracket is 32%. The 5-percentage-point gap is the over-withholding — recovered as a refund at filing in April, but unavailable as cash for the four months between bonus and refund.

The percentage method's flat 22% is, by contrast, a deliberate IRS compromise: it's slightly higher than the 12% bracket where most workers sit, slightly lower than the 24% bracket where most professionals sit. For an employee in the 22% or 24% bracket, the percentage method withholds about right. For an employee in the 32-37% bracket, the percentage method under-withholds, and the aggregate method (or a Q4 estimated payment) makes up the difference.

State Withholding: Most States Mirror, Some Don't

State supplemental rates follow the federal method choice in most states. When the employer runs the federal percentage method on a separate check, most states apply their own flat supplemental rate to that bonus:

• California: 10.23% on bonuses (6.6% on stock options has separate rules)
• New York: 11.7% on supplemental wages above $1M, 9.65% below
• New Jersey: 5% supplemental flat (varies by wage level)
• Illinois: 4.95% flat (matches state regular rate)
• Texas, Florida, Washington, Nevada, South Dakota, Wyoming, Alaska, Tennessee, New Hampshire: no state income tax, no supplemental withholding

States that use aggregate-only withholding (notably Mississippi for some categories, and a few others depending on the wage type) re-run the combined paycheck through state tables the same way the federal aggregate method does. Plug your specific state into the bonus tax calculator to see the combined federal-plus-state hit for your method, or read the full state-by-state breakdown for the 2026 supplemental rates.

How to Read Your Paystub and Know Which Method Hit You

Open your most recent bonus paystub. Look for these signals:

1. Single line for federal withholding equal to exactly 22.0% of the bonus. Percentage method, below $1M YTD.
2. Federal withholding equal to exactly 37.0% of the bonus. Percentage method, above $1M YTD (or your employer is treating you as a covered employee under the executive comp rules).
3. Federal withholding at 28%, 30%, 33%, or any non-flat percentage. Aggregate method. The percentage reflects the table-lookup projection of your combined paycheck through the Pub 15-T tables.
4. Bonus and regular wages on the same gross line, with a single combined withholding figure. Aggregate method (required when paid as a single combined check).
5. Two separate checks issued the same day — one regular, one labeled “Bonus” or “Supplemental.” Almost always percentage method on the supplemental check.

What to Do If the Method Hurts You

If the aggregate method over-withheld and you need cash now: file a new W-4 with your employer claiming additional allowances on Step 4(b) (deductions) for the rest of the year. This reduces withholding on your remaining regular paychecks to offset the bonus over-withholding. Stay below the safe-harbor floor (110% of last year's total tax for high earners) to avoid penalties.

If the percentage method under-withheld and you're in a high bracket: make a quarterly estimated tax payment via Form 1040-ES before the next deadline (April 15, June 15, September 15, January 15). The IRS's safe-harbor rule (Treas. Reg. § 1.6654-2) shields you from underpayment penalties if you pay 100% of last year's total tax (110% if your prior-year AGI was over $150,000) through any combination of withholding and estimates.

If you have negotiating room before the bonus is paid: ask payroll which method they'll use and request the percentage method on a separate check if you'd rather get the cash now and reconcile at filing. Most employers will accommodate one-off requests; some run inflexible payroll systems that bundle bonus with the December paycheck and lock you into aggregate.

The Bottom Line

The percentage method and the aggregate method produce identical final tax liability on your Form 1040 in April. They differ only in when the IRS gets the money — and how much cash you have on bonus day. The percentage method's flat 22% is friendlier to high earners with one-off bonuses; the aggregate method's table projection is friendlier to the IRS, especially when a bonus is bundled into a regular paycheck and the combined gross is annualized into a high-marginal-rate projection.

Knowing which method your employer uses lets you plan cash flow, time large purchases, and decide whether to file a mid-year W-4 update. Run your specific bonus through the PayScale Pro bonus calculator with both methods to compare. For the broader bonus taxation picture, the why-bonuses-look-smaller explainer and the supplemental wages deep-dive cover the rest of the supplemental wage rules.

If you're an hourly worker or freelancer trying to budget around a bonus or one-off project payment, the TDEE calculator at our sister site CalcFit is handy for the related question of how much you actually need to spend each month — and our freelance hourly rate calculator handles the income-side math.